Add ioeventfd and iothread to virtio framework. When a virtio device
claim to support iothread, virtio framework will register a ioeventfd
and add it to iothread's epoll. After that, the new notify will come
through the iothread instead of the vcpu thread. The notify handler will
be called to process the request.
Tracked-On: #7940
Signed-off-by: Conghui <conghui.chen@intel.com>
Acked-by: Wang, Yu1 <yu1.wang@intel.com>
fa69f79e33